Research ArticleAqueous Root Bark Extract of Daniellia oliveri (Hutch. & Dalz.)(Fabaceae) Protects Neurons against Diazepam-InducedAmnesia in Mice

Galba Jean Beppe, Lea Blondelle Kenko Djoumessie, Eglantine Keugong Wado ,HerveHerve NgatankoAbaıssou, BalbineKamleuNkwingwa, Jorelle LindaDamoKamda,Roland Rebe Nhouma, and Harquin Simplice Foyet

Department of Biological Sciences, Faculty of Science, University of Maroua, P.O. Box 814, Maroua, Cameroon

Correspondence should be addressed to Harquin Simplice Foyet; fharquins@gmail.com

Received 5 April 2020; Accepted 23 June 2020; Published 21 July 2020

Guest Editor: Saheed Sabiu

Copyright © 2020 Galba Jean Beppe et al. )is is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Daniellia oliveri (DO) is a traditional medicinal plant used for the treatment of diseases such as inflammation, schizophrenia, andepilepsy in Nigeria, Kenya, Congo, and Cameroon. )is study was carried out to evaluate the potential neuroprotection effect ofthe aqueous root bark extract of Daniellia oliveri against diazepam-induced amnesia in mice. )irty-six adult male mice weredistributed into six groups: the three test groups received Daniellia oliveri root bark extract (100, 200, and 300mg/kg), the normalcontrol group received distilled water (10ml/kg), a positive control group received piracetam (150mg/kg), and the negativecontrol received diazepam (2.5mg/kg). Learning and memory were evaluated using the radial arm maze and the T-maze.Biomarkers of oxidative stress were also quantified in mice brains. Statistical analyses were performed using two-way ANOVAfollowed by Tukey’s post hoc test.Daniellia oliveri root bark aqueous extract decreased the number of working memory errors andnumber of referencememory errors in amnesic mice evaluated in the radial armmaze. Also, an increase in glutathione activity anda decrease in malondialdehyde levels were noted in the hippocampi homogenate of the extract-treated mice as compared to thediazepam-demented but untreated group. Moreover, pretreatment with Daniellia oliveri aqueous root bark extract reversed thedecrease in hippocampal cell density observed in the nontreated diazepam group. Taken together, these results suggest that theaqueous extract of DO leaves possesses antioxidant potential and might provide an opportunity for the management of neu-rological abnormalities in amnesic conditions.

1. Introduction

Amnesia is a neuropsychological pathology which results inthe partial or total loss of memory. )e pathology occurswhen complex neurobiological processes, involved inlearning and short- or long-term storage of information, aredisrupted [1]. It is the main cause of dementia syndrome,which accounts for at least 70% of the cases [2]. )e dis-tribution of the new cases has reached 4.9 million (49%) inAsia, 2.5 million (25%) in Europe, 1.7 million (18%) inAmerica, and 0.8 million (8%) in Africa [2]. Cameroon is notimmune to this pathology with a prevalence of 2.85% in the

city of Yaounde [3]. Causes of this pathology are poorlyknown until now; however, age, environmental, and geneticfactors are considered as risk factors to the occurrence of thisdisease.

Diazepam (DZP) is a benzodiazepine (allosteric mod-ulators GABA receptor) which is well tolerated in organismand employed in the treatment of memory disorders, psy-chomotor disorders, sedation, dependence, and anxietyrebound [4]. Acute administration of DZP causes antero-grade amnesia [5], while intravenous administration sig-nificantly impairs free recall based on the dose used [6].Pretreatment with diazepam (2.0–16.0mg/kg i.p.) or

HindawiEvidence-Based Complementary and Alternative MedicineVolume 2020, Article ID 7815348, 9 pageshttps://doi.org/10.1155/2020/7815348

scopolamine (3.0mg/kg i.p.) causes an alteration of theanterograde memory, in a dose-dependent manner [4, 7].According to Maria et al. [8], intraperitoneal injection (i.p.)of 2.5mg/kg DZP induces amnesia in rodents by hyper-polarization of neurons, decreased excitability, and in-creased lipid peroxidation [9, 10]. )e current treatmentoptions, such as surgery and synthetic drugs, are limited intheir ability to improve neuronal function because they failto repair damaged neurons or improve neural regeneration[11]. Due to the adverse side effects of standard antiamnesicdrugs line, rivastigmine, donepezil, and galantamine, al-ternative therapies consisting of plant-derived medications,are increasingly being used to relieve neurodegenerativedisorders [12].

Daniellia oliveri is a plant which grows in the Amazonia,certain part of America, and some Africans countries in-cluding Cameroon. Roots of this plant are used in traditionalmedicine to treat anxiety and schizophrenia [13]. Leavesdecoction and stem bark infusion have been used as diureticand aphrodisiac and applied as skin lotion. Dry leavespowder is also administered to treat yellow fever, back ache,and headache and for wound healing. )e dried root andstem bark have been used in Ivory Coast as chewing stickand the water extract of the stem bark showed antibacterialactivity [14]. Hexane and methanolic extracts of the barkshowed analgesic and anti-inflammatory activities, while themethanolic extract of the stem bark showed smooth musclerelaxant activity [15]. Gaston and Daget [16] reported thepresence of glycosides, flavonoids, saponins, rutin, querci-trin, and quercimeritrin in leaves. Saponins and flavonoidsare recognized as anti-inflammatory and antioxidant com-pounds which could impart many health benefits andthereby reduce the risk of many chronic illnesses like de-generative disorder [17, 18]. )is study was carried out toinvestigate the neuroprotective effects of D. oliveri root barkaqueous extract, in the diazepam-induced amnesia (DZP)mouse model.

2. Materials and Methods

2.1. Chemicals. Diazepam, acetylthiocholine iodide, 5,5-dithiobis (2-nitro-benzoic acid) (DTNB), 2-thiobabituricacid (TBA), and piracetam were purchased from Sigma-Aldrich, USA. All drugs and extracts were freshly preparedin saline on the day of experiments.

2.2. Plant Material and Plant Extract. Daniellia oliveri rootbark was collected in Lara (Far North Region, Cameroon) inthe month of December 2017 and authentificated at theNational Herbarium, Yaounde, where a voucher specimenwas deposited under the reference number 14890/SRF/Cam-YA. After collection, Daniellia oliveri (DO) root bark wasshade-dried for 5 days and pulverized into a fine powder.)e extraction procedure used was as previously describedby Soro et al. [19]. Briefly, 150 g pulverized sample materialwas introduced in 1 L of distilled water and boiled for30min. )e filtrate was passed through a Whatman filterpaper N° 4 and the solvent was eliminated from the extract

using a temperature controlled oven (50°C for 24 hours).)epowder obtained was weighed and the extraction yield wasdetermined (1.85%).

2.3. Experimental Animals. Adult male Swiss mice aged 3months (weighing 18–26 g) were obtained from the NationalVeterinary Laboratory of Garoua, Cameroon. Mice wereacclimatized for 14 days, housed in polyacrylic cages (6animals/cage) under natural dark-light cycle and providedwith water and food ad libitum. Prior to and after treatment,mice were fasted for 12 and 7 h. Animal treatment and carewas in accordance with the guidelines of the CameroonianBioethics Committee (Reg N° FWA-IRB00001954) andfollowing NIH-Care and Use of Laboratory Animals Manual(8th Edition). Each animal was tested in only one behavioraltest and tests were made to minimize animal suffering.

Mice were randomly divided into 6 groups of 6 animalseach and subjected to the following treatment schedule(Figure 1).)e normal control group received distilled water(DW) only (10mL/kg p.o.), the negative control group re-ceived a single administration of diazepam (2.5mg/kg,i.p. + DW) on day 14, the positive control group received asingle dose of piracetam (150mg/kg, p.o.), and different testgroups received extract (DZP+ 100, 200, and 300mg/kg p.o.of DO) for 14 days. Diazepamwas administered to all groupsexcept the normal control 30 minutes after treatment on day14. Behavioral tests were launched 30 minutes after diaze-pam administration.

2.4. Behavioral Test

2.4.1. Radial Arm Maze Task. )e radial arm maze used inthe present study consisted of eight arms, numbered from 1to 8 (48 cm× 12 cm), extending radially from a central area(32 cm in diameter). )e apparatus was placed 50 cm abovethe floor. At the end of each arm, there was a food cup thathad a single 50mg food pellet. Before the performance of themaze task, animals were kept on restricted diet designed tokeep their body weight at 85% of their free-feeding weightover a week, with water being available ad libitum. Before theactual training began, each mouse was simultaneouslyplaced in the radial maze and allowed to explore for 5minand take food freely. )e food was initially availablethroughout the maze but was gradually restricted to the foodcup. )e animals were trained for 7 days to run to the end ofthe arms and consume the bait. )e animals were trained formaze task performance by conducting daily training trialsfor 5min, during which they do not receive any drug. )etraining trial continued until all the 4 baits had been con-sumed or until 5min had elapsed. Completely trained an-imals were chosen for the study. Briefly, each animal wasplaced individually in the center of themaze and subjected toworking and reference memory tasks, in which the samefour arms (1, 3, 5, and 7) were baited for each daily trainingtrial. )e other four arms (2, 4, 6, and 8) were never baited.An arm entry was counted when all four limbs of the mousewere within an arm. Measures were made on the number ofworking memory errors (entering an arm containing food,

2 Evidence-Based Complementary and Alternative Medicine

but previously entered) and reference memory errors (en-tering an arm that was not baited). )e time taken toconsume all four baits was also recorded. Reference memorywas regarded as a long-term memory for information thatremains constant over repeated trials (memory for thepositions of baited arms), whereas working memory wasconsidered a short-term memory in which the informationto be remembered changes in every trial (memory for thepositions of arms that had already been visited in each trial)[20].

2.4.2. T-Maze Task. )e T-maze test evaluates the ability ofthe rodent to memorize its first choice. It is a behavioralapproach to study the following aspects of cognition: al-ternation behavior, location recognition, object recognition,spatial discrimination, working memory, and referencememory which is measured here [21]. )e T-maze used inthis study consisted of a T-shaped device, made of wood,painted white. It consists of a departure compartment andtwo arrival arms 30 cm long, 10 cm wide, and 25 cm high.Aluminum doors were placed at the exit of the departurecompartment and at the entrance of each arrival corridor tocontrol access to the various areas of the maze. At the end ofeach arrival compartment was a small cup containing a bait.

Two days before the start of the experiments, animalswere progressively deprived of food to maintain them at 85%of their weight. Mice were placed one after the other in thestarting arm of the T-maze. After each trial, the maze wascleaned with 70% ethanol, to eliminate residual odours leftby the preceding mice. )is test was carried out over threedays during which habituation, acquisition, and retentionphases were assessed each day, respectively [21].

)e habituation phase consisted of a single session offree-choice trial. A mouse was placed in the start arm andallowed to explore the maze for 5min. )e preferred anddiscriminated arms of each mouse were noted. During theacquisition phase which was performed the next day, mice

were subjected to a forced-choice trial. )e discriminatedarm was blocked by a guillotine door. Once the animal wasreleased from the starting arm, it was allowed to explore themaze by entering the preferred arm and returning to thestart arm. During retention, all the guillotine doors wereopened and mice were free to explore all the arms. In all thesessions, each mouse was evaluated for 5min and the timespent in arms and number of returns to start arm wererecorded. )e floor of the apparatus was cleaned with 70%ethanol between trials to eliminate olfactory cues [22].

2.5. Biochemical Assay. After the behavioral tests, all micewere deeply anesthetized (using sodium pentobarbital,100mg/kg b.w., i.p.) and decapitated and whole brains wereremoved. )e hippocampus was carefully excised. )ehippocampal sample was homogenized (1 :10) in ice-cold0.1M phosphate buffer (pH 7.4). )e homogenate wascentrifuged (15min) and the supernatant was used toevaluate malondialdehyde (MDA) and reduced glutathione(GSH) levels.

2.5.1. Determination of MDA. )e level of lipid peroxideswas measured by thiobarbituric acid reaction previouslydescribed by Ohkawa et al. [23]. 200 μL of supernatant addedand briefly mixed with 1mL of 50% trichloroacetic acid in0.1M HCl and 1mL of 26mM thiobarbituric acid after thevortex mixing sample was maintained at 95°C for 20min.Furthermore, samples were centrifuged at 9609 rpm for10min and supernatants were read at 532 nm. A calibrationcurve was constructed using MDA as standard and theresults were expressed as nmol/organ of tissues.

2.5.2. Determination of GSH. It was measured following themethod described by Fukuzawa and Tokumura [24]. 200 μLof supernatant was added to 1.1mL of 0.25M sodiumphosphate buffer (pH� 7.4) followed by the addition of

Biochemical assays and histological sections

36 mice (6/group)

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Figure 1: Experimental design. NC�neutral control, DW� distilled water, D� days, DO�Daniellia oliveri, and RAM� radial arm maze.

Evidence-Based Complementary and Alternative Medicine 3

130 μl DTNB 0.04%. Finally, the mixture was brought to afinal volume of 1.5mL with distilled water and absorbancewas read in a spectrophotometer at 412 nm and results wereexpressed as μg GSH/μg organ.

2.6. Histology of the Tissues. On day 14, after the acquisitionof hippocampi, whole brains were collected, fixed in 10%formalin for a week. Fifty (50) mm coronal sections weremade from the brain in the hippocampus region using theMouse Brain Atlas with the following coordinate (anterior/posterior D 2.0mm, medial/lateral D 1.5mm, and dorsal/ventral AP D 2.0mm) [25]. Hippocampi sections werecollected in nine-well plates. )e dehydration of thesesections consisted in introducing tissues in ascendingconcentrations of ethanol followed by immersion in xyloland then embedding in paraffin. Paraffin sections of thebrain were deparaffinised and rehydrated through washes indescending concentration series of alcohol. Hippocampiwere then stained using hematoxylin and eosin stains. )ebrain sections were thereafter photographed and imageswere captured using a digital camera attached to a lightmicroscope (Scientico, Haryana, India).

2.7. Statistical Analysis. All the results were expressed asmean± SEM. )e data were analyzed by one-way ANOVA(T-maze) and two-way ANOVA (RAM) followed by Tukeyand Bonferroni post hoc tests, respectively. All analyses wereperformed using Graph Pad Prism 5.00 software, San Diego,California, USA. Results were considered significant atp< 0.05.

3. Results

3.1. Effect of D. oliveri Root Bark Aqueous Extract onWorkingand Spatial Reference Memory in the Radial Arm Maze.To investigate whether the aqueous extract of D. oliveri (100,200, and 300mg/kg) affects spatial memory formation, themice were evaluated in the radial arm maze task. For ref-erence memory errors, ANOVA revealed a significant timedifference (p< 0.01) (Figure 2). Additionally, Tukey’s posthoc analysis revealed significant differences between thenormal control and DZP groups (p< 0.01), normal controland DZP+DO (100mg/kg) groups (p< 0.01), DZP andDZP+DO (200mg/kg) groups (p< 0.01), and DZP andDZP+DO (300mg/kg) groups (p< 0.01). )ere were nosignificant differences between different doses of extract(p> 0.05). Moreover, the time taken to consume all the baitssignificantly increased (p< 0.001) in untreated mice com-pared to the normal control group (Figure 3). )e admin-istration of D. oliveri root back aqueous extract significantly(p< 0.001) reduced this time in DZP+DO (100mg/kg)groups (p< 0.001), DZP+DO (200mg/kg) groups(p< 0.01), and DZP+DO (300mg/kg) groups (p< 0.001)compared to DZP group.

For working memory errors, Tukey’s post hoc analysisrevealed significant differences between the normal controland DZP groups (p< 0.001), DZP and DZP+DO (100mg/kg) groups (p< 0.001), DZP and DZP+DO (200mg/kg)

groups (p< 0.001), and DZP and DZP+DO (300mg/kg)groups (p< 0.001) on the 7th day of the treatment (Figure 4).

3.2. Effect of D. oliveri Root Bark Aqueous Extract on Long-Term Memory in T-Maze Task. )e T-maze test was per-formed to confirm the potential effect of DO on long-termmemory. ANOVA revealed that acute administration ofdiazepam significantly (p< 0.05) increased the time spent inthe preferred arm as compared to the control group (Fig-ure 5). Animals treated with D. oliveri aqueous extract200mg/kg for 14 days resulted in a significant (p< 0.05)increase of this time in the preferred arm compared todemented group. )e treatment of animals with piracetamsignificantly increased (p< 0.001) the time spent in pre-ferred arm in comparison with the untreated group. Inaddition, the number of returns in the starting arm increasedsignificantly (p< 0.001) in untreated animals compared tothe normal control ones (Figure 6). It was also observed thatthe administration of D. oliveri root bark aqueous extract,100 and 200mg/kg, significantly (p< 0.001) reduced thesenumbers as compared to the untreated group. No significant(p> 0.05) difference was noted with the 300mg/kg doses ofthe extract.

3.3. Effect of DO on MDA Content and Reduced GSH Level.Brain malondialdehyde (MDA) concentration was signifi-cant (p< 0.001) in the negative control group mice com-pared to the normal control (Figure 7(a)). )e treatment ofthe animals with the aqueous extract of D. oliveri at dose of100mg/kg for 14 days significantly (p< 0.01) reduced theconcentration of MDA compared to animals receivingdiazepam.

)e hippocampal concentration of malondialdehyde wassignificantly (p< 0.001) decreased in the animals treatedwith piracetam in comparison with the untreated group.

Glutathione concentration (GHS) decreases nonsignif-icantly (p> 0.05) in the group of mice that received diaz-epam with respect to normal control mice (Figure 7(b)). )epretreatment of mice with Daniellia oliveri root barkaqueous extract 200mg/kg for 14 days significantly(p< 0.001) increased this concentration in comparison withthe demented group. )is parameter was also increasednonsignificantly (p> 0.05) in animals that were givenpiracetam compared to the demented group which was notsubjected to any treatment.

3.4. Effects of Daniellia oliveri on Hippocampi HistologicalSections. )e effects of Daniellia oliveri aqueous root barkextract administration on the micromorphology of thehippocampus are illustrated in Figure 8. )e analysis of thehistological sections performed shows that in animalstreated with DZP and receiving distilled water, the layer ofgranular cells at the dentate gyrus exhibits an abnormalarchitecture with some signs of cellular degeneration (redarrow) compared to that of the healthy control. In animalstreated with DZP but did not receive the plant extract atdoses of 100 and 300mg/kg, the coronal sections revealed a

4 Evidence-Based Complementary and Alternative Medicine

normal architecture. However, signs of cellular degenerationstill persist in the coronal section of animals treated withplant extract at a dose of 100mg/kg.

4. Discussion

)e aim of this study was to evaluate the neuroprotectiveeffects of the aqueous extract of Daniellia. oliveri root barkon diazepam-induced amnesia model in mice. To achievethis, behavioral tests such as the radial maze and the T-mazewere used, oxidative stress parameters (malondialdehydeand reduced glutathione) were evaluated in hippocampi

homogenates, and the histological sections of the hippo-campus were performed.

Diazepam is an anxiolytic and hypnotic which binds toGABA-A receptors to exert its effects [26, 27]. However, itis possible to experimentally induce amnesia, which iseither temporary (in the case of episodic memory) or re-versible (for semantic memory) with benzodiazepines [28].)e results of this work show an increase of the number ofreference memory errors (entering an arm that was notbaited) and working memory (entering an arm containingfood, but previously entered) in diazepam-treated animalscompared to animals in the neutral control group in the

Normal controlNegative controlDZP + PIR 150

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Figure 2: Effect of the aqueous extract ofD. oliveri root on the referencememory of amnesic mice in the radial maze test. Each bar representsthe mean±ESM, n� 6. £££p< 0.001� significant difference compared to the normal control; §p< 0.05 and §§§p< 0.001� significant dif-ference compared to negative control. DZP 2.5 +DW� diazepam (2.5mg/kg) + distilled water; PIR 150� piracetam (150mg/kg); DO 100,200, 300�Daniellia oliveri (100, 200, 300mg/kg).

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Figure 3: Effects of the aqueous root extract ofD. oliveri on the time taken to consume the baits in the radial maze test. Each bar represents themean±ESM, n� 6. §§§p< 0.001� significant difference compared to the negative control. DZP 2.5 +DW� diazepam (2.5mg/kg) + distilledwater; PIR 150� piracetam (150mg/kg); DO 100, 200, and 300�Daniellia oliveri (100, 200, 300mg/kg).

Evidence-Based Complementary and Alternative Medicine 5

radial maze. Also, an increase was noted in the number ofreturns to the starting arm and a decrease of the time spentin the preferred arm in the diazepam-treated animalscompared to the neutral control animals when they weresubjected to the T-maze test. An increment in the timespent in the discriminated arm and a decrement in the timespent in the preferred arm are indications of impairedmemory [29]. )ese observations were completely reversed

by pretreatment with the aqueous extract ofD. oliveri for 14days. In fact, in the radial maze test, the aqueous extract ofD. oliveri roots bark at different tested doses significantly(p< 0.001) reduced the number of working and referencememory errors, thus translating an improvement of theworking and reference memory, respectively, in amnesicmice. In addition, there was a decrease (p< 0.001) in the

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Figure 4: Effects of the aqueous extract ofD. oliveri root bark on the number of working memory errors on in the radial maze test. Each barrepresents the mean± ESM, n� 6. £££p< 0.001� significant difference compared to the normal control; §§§p< 0.001� significant differencecompared to the negative control. DZP 2.5 +DW� diazepam (2.5mg/kg) + distilled water; PIR 150� piracetam (150mg/kg); DO 100, 200,and 300�Daniellia oliveri (100, 200, and 300mg/kg).

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Figure 5: Effects of the aqueous extract ofD. oliveri roots on the timespent in the preferred arm of the T-maze test. Each bar represents theaverage±ESM, n� 6. §p< 0.05 and §§§p< 0.001� significant dif-ference compared to negative control. DZP 2.5 +DW� diazepam(2.5mg/kg) + distilled water; PIR 150� piracetam (150mg/kg); DO100, 200, and 300�Daniellia oliveri (100, 200, and 300mg/kg).

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Figure 6: Effects of the aqueous extract of D. oliveri roots on thenumber of starting arm return of the T-maze test. Each bar rep-resents the mean±ESM, n� 6. £££p< 0.001 significant differencecompared to the normal control; §§§p< 0.001 and §p< 0.05 sig-nificant difference compared to negative control. N con-trol� normal control; DZP 2.5 +DW� diazepam (2.5mg/kg) + distilled water; PIR 150� piracetam (150mg/kg); DO 100,200, and 300�Daniellia oliveri (100, 200, and 300mg/kg).

6 Evidence-Based Complementary and Alternative Medicine

time taken to consume all baits. Moreover, in the T-maze,the results obtained show a significant increase (p< 0.05) inthe time spent in the preferred arm and a significant de-crease (p< 0.001) in the number of returns to the startingarm with all the doses of the extract. According to Cha-pouthier et al. [30], the increase in the time spent in the

preferred arm and a reduction in the time spent in thediscriminated arm reflect a good functioning of thememory. Furthermore, Farshchi et al. [29] reported that adecrease in the number of returns to the starting armsuggests an improvement in memory. )ese observationssuggest that the aqueous extract of D. oliveri roots could

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Figure 7: Effects of the aqueous extract of the root bark ofDaniellia oliveri on the brain concentration of MDA (a) and reduced glutathione(b). Each bar represents the mean±ESM, n� 6. £££p< 0.001; significant difference compared to the normal control; §p< 0.05, §§p< 0.01, and§§§p< 0.001; significant difference compared to the negative control. DZP 2.5 +DW� diazepam (2.5mg/kg) + distilled water; PIR150� piracetam (150mg/kg); DO 100, 200, and 300�Daniellia oliveri (100, 200, and 300mg/kg).

CA1

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Figure 8: Effects of D. oliveri extract on hippocampi sections of mice brains. Coronal sections: hematoxylin and eosin-40x magnification;CA� cornus ammonis, GD� dentate gyrus, and HGD: dentate gyrus hilus. Yellow arrow: stratum oriens; green arrow: layer of pyramidalcells (contains the cell bodies of the pyramidal cells of the cornus ammonis. )e density of the blue color corresponds to the density of thecell bodies of pyramidal neurons); blue arrow: stratum lacunosum-moleculare (contains pyramidal cell segments); black arrow: molecularlayer of the dentate gyrus. ML: molecular layer of dentate gyrus. (a) Normal (DW 10ml/kg). (b) DZP 2.5mg/kg +DW. (c) DZP+PIR150mg/kg. (d) DZP+DO 100mg/kg. (e) DZP+DO 200mg/kg. (f ) DZP+DO 300mg/kg.

Evidence-Based Complementary and Alternative Medicine 7

play an important role in memorization and more spe-cifically by improving short-term and long-term memory.Pervious study has reported the presence of saponins,flavonoids, tannins, and alkaloids in the extract of D.Oliveri. )ese compounds are endowed with numerouspharmacological properties [16]. Indeed, Diaby [31]demonstrated that the aqueous extract of Daniellia oliveribark had antiepileptic properties. In addition, the oleoresinisolated from this plant is an anti-inflammatory and an-tioxidant agent [32]. )erefore, the neuroprotective effectof this extract could be attributed to these groups ofcompounds. In order to elucidate how the extract act, theaqueous extract of the root bark of Daniellia oliveri, bio-chemical assays were carried out in homogenates of thehippocampus of amnesic mice.

DZP induces amnesia by generating reactive oxygenspecies [7]. )e brain has increased susceptibility to oxi-dative stress because it contains high concentrations ofpolyunsaturated fatty acids vulnerable to lipid peroxidationand also has modest antioxidant capacity [33]. In addition,the high oxygen consumption in the brain, the metabolismof catecholamines, and the release of neurotransmitters areconsidered as important sources of free radicals and aretherefore associated with significant oxidative damage [4].Free radicals and related molecules are often classified to-gether as reactive oxygen species (ROS) [33]. )e formationof ROS in nerve cells is numerous, so cells must maintain aneffective antioxidant system to protect against the overloadof ROS and the resulting damage [7]. During oxidativestress, the production of ROS increases and exceeds thecapacity of endogenous free radical scavengers such as GSH,CAT, and SOD [9, 10]. It has also been reported that ROSformation is involved in the neurotoxicity of many xeno-biotics [4]. In this research, diazepam caused a significantchange in the MDA content and GSH activities in thehippocampus. )is observation was completely reversed bythe pretreatment of animals with DO extract. However,concomitant administration of D. oliveri and diazepam notonly reduced MDA concentration but also increased GSHconcentration and enzymatic activity in the hippocampus ofmice. GSH, CAT, and SOD are major enzymes that fight freeradicals in the body. Indeed, GSH is vital for detoxifyingheavy metals; the thiol group reacts with the salts of theseheavy metals, creating with them a very strong sulfur-metalbond so that they are subsequently excreted without causingany harm to the organism [34]. )e observed effect may bedue to the radical scavenging properties of flavonoidscontained in D. oliveri. )e present results thus demon-strated the correlation between the antiamnesic effects of theaqueous extract of D. oliveri root bark against diazepam-induced amnesia and its antioxidant capacity.

Neurons provide the transmission of a bioelectric signalcalled nerve impulse. )ey have two physiological proper-ties: excitability, that is, the ability to respond to stimuli andconvert them into nerve impulses and conductivity, that is tosay, the ability to transmit impulses nervous [35]. Anydisturbance (degeneration) of a neuron at the level of thehippocampus leads to difficulty or inability to learn [36].)ehistological section results showed a decrease in the density

of the neurons of animals in the group receiving only di-azepam compared to animals in the neutral control group. Incontrast, DO (300mg/kg) treated animals’ hippocampi wereprotected from cell death associated to diazepam adminis-tration. )e aqueous extract of D. oliveri root barks at a doseof 300mg/kg therefore protects the neurons against diaze-pam-induced amnesia in mice. )e aqueous extract of D.oliveri root bark could therefore act either as a DZP receptorantagonist or by inhibiting lipid peroxidation while in-creasing the antioxidant status. All these properties would beattributable once again to the various compounds (glyco-sides, flavonoids, rutin, quercitrin, tannins, saponins, andglycosides) contained in this plant. Stud phytochemicalscreening is still going on to identify and specify thecompounds responsible of the observed effects.

5. Conclusion

)e present study strongly demonstrates that D. oliveriroot bark aqueous extract of 200 and 300mg/kg effec-tively enhances memory processes, restores antioxidantbrain status, and may confer neuroprotection by thealleviation diazepam-induced oxidative damage. )eseresults suggest that the aqueous extract of D. oliveri rootbark may possibly be used as a promising natural productfor the prevention of memory disorders. )e result of thisstudy supports the traditional claim of the plant’s use forschizophrenia, epilepsy, and studies currently beingconducted to delineate the toxicological profile of thisplant.

Data Availability

)e data used to support the findings of this study areavailable from the corresponding author upon reasonablerequest.

Disclosure

)is work was carried out at the Laboratory of the De-partment of Biological Sciences, Faculty of Sciences, Uni-versity of Maroua, Cameroon.

Conflicts of Interest

)e authors declare that they have no conflicts of interestrelated to the publication of this study.

Acknowledgments

)e authors are grateful to the head of the Laboratory ofthe Department of Biological Sciences, Faculty of Sci-ences, University of Maroua, Cameroon, for providingthe facilities. )e authors are also grateful to the head ofthe Laboratory of Animal Physiology, Department ofBiology and Animal Physiology of the Faculty of Sciences,University of Yaounde, Cameroon, for providing facili-ties for histological studies.

8 Evidence-Based Complementary and Alternative Medicine

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